The design and development of thermal insulating materials, is an extensive art. Many systems have been developed employing, as the major insulating materials, various fibrous and powder products. There have also been a variety of ways for utilizing these materials, including the use of evacuated shells and bags, compression of the insulating materials, and varying orientations of the insulating materials.
Two of the most widely used thermal insulation materials are fiberglass and polyurethane foam. It is generally accepted that the thermal insulation quality of fiberglass is less than that of polyurethane foam. One advantage of fiberglass, however, is that it may be used as a thermal insulation in environments that involve rather high temperatures, that is above 150.degree. F. Polyurethane foam on the other hand, while having a better thermal insulation quality than fiberglass, is detrimentally affected as an insulator when subjected to temperatures above 150.degree. F. Therefore, these materials have both advantages and disadvantages.
In our copending application Ser. No. 699,930, filed Feb. 8, 1985, now U.S. Pat. No. 4,636,415, entitled "Precipitated Silica Insulator," assigned to the same assignee as the present invention, we have described the use of precipitiated silica as an insulator to achieve good insulating properties at relatively low cost. The precipitated silica, in accordance with that application, is dried at a temperature sufficient to drive off the surface water, is then compressed, placed in a gas and water tight envelope which is evacuated, and the gas and water tight pouch then sealed.
While the insulation formed with precipitated silica, as just described, is perfectly adequate, it would be extremely desirable to be able to obtain the same properties at a lower cost. By this invention a material is provided that accomplishes this desirable result and, at the same time, has better thermal insulation properties than fiberglass and can withstand elevated temperatures that would detrimentally affect polyurethane foam.